Methods: This longitudinal in situ study was performed in two phases: 1. Test of brushing effect, using parallel-group design (n=5); 2. Test of fluoride effect, using cross-over design (n=10). In phase 1, 15 subjects, divided among three different regimens, had enamel specimens placed in their lower partial dentures and tested for 28 days: A. Erosion only, B. Erosion+toothbrushing with fluoridated dentifrice (1,100 ppm F, as NaF) and C. Erosion+toothbrushing with non-fluoridated dentifrice (0 ppm F). Erosion consisted in the immersion of the dentures in grapefruit juice 4x/day, for 5min. For groups B and C, brushing was performed 5min after erosion for 20s, with an electric toothbrush and the test dentifrices. In phase 2, subjects of groups B and C switched treatments (cross-over) and repeated the same experimental protocol. In both phases, subjects were examined every 7 days, when: adverse events and diet diary were checked and recorded; experimental procedures were reviewed; and enamel surface loss was determined by optical profilometry of impressions taken from the specimens.
Results: Four outliers, with extreme enamel loss, were identified and excluded from the analyses. In phase 1, no significant differences were observed among regimens (p=0.07), for any of the studied periods (p=0.55). In phase 2, higher enamel wear was observed for C than B (p=0.003). In both phases a significant trend was observed for the increase of enamel wear through the experiment (p<0.05).
Conclusion: The development of erosion-abrasion lesions seemed to be affected by biological inter-subject variations. The long-term model was able to provide adequate responses for the erosive, erosive-abrasive and fluoride effects. Fluoridated dentifrice reduced the development of erosive-abrasive lesions.
Supported by GlaxoSmithKline.